I am sure Mark wanted to do this for quite some time. Community Notes have been a way to let the audience do the fact checking for them, in exchange for a "sense of pride and accomplishment" instead of paying millions or billions to vendors and alienate half of its audience. The timing is obviously to placate Trump.

The effectiveness of Community Notes is up to debate. Though I personally have seen some really brutally honest or hillarious fact checks (check out Community Notes Violations on Twitter) but I still feel it can be brigaded by trolls to say the inverse is the truth. I have an anecdotal example from recent memory which on a post of someone commenting on the new Superman trailer, with a shot of Corenswet as Clark Kent gushing about how much he looked like Superman. I saw a humorous community note on that post that claimed the person in the image is not Superman but Clark Kent and they are separate people.

To me this raises the question, couldn't Community Notes potentially be overwhelmed by trolls to claim a falsehood as the truth for more nefarious reasons (this may have happened already, though I have not seen it yet).